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  • Writer's pictureEinar Páll Svavarsson

A story of a new volcano and how it started

Geldingadalir eruption first day
The second day of the eruption at Geldingadalir valley in Mt. Fagradalsfjall

The period from the initial indication that an eruption was likely at Mt. Fagradalsfjall Reykjanes Peninsula up to the time the magma broke through to the surface, tells a fascinating story about volcanic eruptions in Iceland—how a possible eruption is spotted and how the information is communicated to the public. One can also find out how an eruption typically begins in this small volcanic island and observe the deep fascination Icelanders have for eruptions like this one in Geldingadalir.

The long period of earthquakes

Crater on second day at Geldingadalir eruption
Icelanders flocked in thousands in the first days to see the new crater

When increased seismic activity began north of the town of Grindavík at the beginning of 2020, the immediate and common conclusion was an eruption. This possibility was then repeatedly communicated to geologists, who were well prepared in a country where inhabitants live through 20–25 eruptions in a lifetime, on average.

At that time, the scientific community held the unified opinion that the increased activity did not necessarily point to an eruption, at least not in the short run. There were limited signs of magma accumulation in the crust around the center of the earthquakes. Conversely, most scientists also agreed that the situation was unusual and an eruption within a few months, possibly a few years or decades, was not out of the question. Some earth science jargon has been accepted among Icelanders for a long time as regular communication between the public and the scientists where two contradictory options are possible—one being soon, and the other an unclear event in the near or far future.

Visitors by the new crater in Geldingadalir
The new crater and the volcanic activity was a spectacular sight without a doubt

In the months that followed the seismic activity, the Reykjanes Peninsula— including Grindavík, the geothermal powerplant of Svartsengi, and the Blue Lagoon—was hit by severe seismic activity, repeatedly shaken by stronger-than-usual earthquakes. With more seismographs and increased monitoring, a large part of the Reykjanes Peninsula, particularly the Mt. Fagradalsfjall volcanic system and its neighboring valleys, was monitored more thoroughly by the University of Iceland, The Icelandic Meteorological Office (IMO), and various other institutions and companies in the field of geology. For months, everything was unstable and living in the region proved to be stressful for the inhabitants.

The big 5.7 earthquake that changed the mood

Early evening eruption at Geldingadalir
During the eruption, the volcano in Geldingadalir displayed spectacular activity

On February 24th, 2021, at 10:06 AM, a big earthquake of magnitude 5.7 hit. It was felt by everyone in the Reykjavik capital area as well the Reykjanes Peninsula. In a country where powerful natural forces are integrated into our way of life, it didn’t take a lot of imagination to understand that this was a game-changer. When an unusually high number of big quakes and thousands of smaller ones ensued in the following days, it was evident that the situation was serious. Kristín Jónsdóttir, a scientist and seismologist at the IMO and the leader of the group delegated to deal with natural disasters, was assigned the responsibility of liaising with the media. Although experienced in communicating information, her role was now much more challenging—she and her colleagues had to analyze the rapidly accumulating scientific data and respond to questions that were difficult or almost impossible to answer. Furthermore, it was unusual to have such activity so close to the Reykjavik capital area. From Jónsdóttir’s initial answers, it was clear that the possibility of eruption was climbing higher on the list of possible outcomes of this enormous increase in seismic activity.

The possibility of an eruption was also supported by satellite photos showing magma approaching the surface through the crust in a narrow fissure at the Nátthagi valley, in the eastern part of Mt. Fagradalsfjall. It was evident that the magma was drawing closer to splitting the earth apart, making it possible for a glowing stream to surge up to the surface.

The whole nation on alert

Many craters active in the new volcano
At one point, many craters had opened, and the new volcano put on an unbelievable show

Around noon on March 3rd, a period of continuous quakes began, labeled by geologists as a relentless pulse of earthquakes. It pushed all scientists, the entire natural disaster group, and the Department of Civil Protection and Emergency Management to one conclusion: An eruption was imminent, possibly mere hours away. The whole nation was put on high alert. It was a very serious event as it was impossible to predict the fissure's size or the nature or force of the lava flow. Overwhelming facts from prior volcanic activity throughout four centuries, at the time of settlement at the Reykjanes Peninsula, new data from monitoring the area, and satellite photos of the area indicated a relatively small eruption and a fissure that would open at Nátthagi valley. As it was impossible to predict the fissure's length, everyone was asked to stay out of the area.

The nation held its breath as a truckload of earth scientists expressed opinions on social media and various broadcasting services about a possible eruption, staying true to their scientific jargon. Again, the scientific community was reasonably relaxed, and most of our scientists believed that if an eruption occurred, it would be a small lava flow with a limited amount of ash or tephra; no danger to buildings or infrastructure was indicated. However, nothing happened on that day as the magma, despite continuing upwards, kept its place below the surface.

The perfect tourist eruption

In the evening of March 3rd and the days that followed, the nationwide alarm appeared to be a false one. However, about two weeks later, on the evening of March 19th, a small eruption quietly began. It was small in every sense of the word, at least in the beginning. The fissure that opened was less than 500 meters long and looked like a shallow scratch on the surface; a much longer fissure of 5 or even up to 25 kilometers is not unusual in Iceland's geological history. The flow of magma was moderate, about 5 m/sec, just like a small river. The valley where it opened, Geldingadalir, was also unusually small compared to most other valleys in Iceland, which provided only a small hill for the fissure to form. The mountains surrounding the eruption were also all small. In a matter of hours, the opening had delivered lava to both sides of the fissure and quickly formed a crater that became the flowing magma's main vent. The crater and the glowing lava river instantly became a stunning sight as the eruption quietly began laying a carpet of lava at the bottom of the small valley. It was a relief for the geologists handling national disasters that their reasons for a full national alarm a few days earlier had materialized. They were able to predict an eruption reasonably accurately. However, instead of a national disaster, mother nature had delivered only a small eruption. Immediately the outbreak was labeled “tourist eruption,” meaning that it would be a great attraction and easy to visit.

What kind of eruption was it?

Volcanic activity at Geldingadalir during night
Sometimes in the evening or into the night, the experience became surreal as the volcano sprayed glowing lava hundreds of meters into the air

It only took a day or two for the main question directed to the earth science community to switch from “will there be an eruption?” to “how long will the eruption last?” One of the leading geologists at the University of Iceland, Professor Magnús Tumi Guðmundsson, flew over the new eruption in a helicopter and confirmed it to be a tiny one, making the statement that it was just a “little punk” (ræfill, in Icelandic). In the days before the event, Kristín Jónsdóttir had often made a statement that the awaited eruption would probably be short and small. True to their jargon, most earth scientists stated that the event was, on the other hand, most likely the beginning of a long eruption period at the Reykjanes Peninsula, an area that had been dormant for more than 800 years but was highly active for centuries before it calmed down. Although most Iceland regions are well documented in the Sagas, the Reykjanes Peninsula is hardly mentioned, most likely because continuing eruptions at the time of settlement around 950 AD made it almost uninhabitable.

In the first two to three days of the small eruption, there was an analytical void among earth scientists as most of their answers were based on research gathered before the eruption. Most scientists assumed that the magma was a typical basalt magma of 1000°C that had slowly accumulated for centuries in the crust and was now pushing its way to the surface, very much in accordance with the many lava flows that had occurred around the time of settlement, from the 9th up until the 13th century. Just like many recent Iceland eruptions originating in magma chambers fed by the mantel plumb, the giant fireball was placed below our little island. However, then came a surprising fact from the geophysicists who had spooned the new glowing magma at Geldingadalir into a small container with water for analysis: The chemical composition was extremely interesting and another game-changer in the short life of this fascinating event. This magma resembled lava that had surfaced at Reykjanes Peninsula around the end of the Ice Age, around 10 to 14 thousand years ago. It was probably the beginning of a lava shield, just like its neighbor (hold your breath) Þráinsskjöldur, a vast lava shield that emerged in a long and slow eruption around 13 thousand years ago. It did not resemble the chemical composition of the lava that surfaced around the settlement, and the temperature was much higher, about 1200°C. This meant that the lava came from a deeper source, about 20 kilometers deep—from the mantle. It also meant that the small eruption could last for (and now the geological jargon came in handy) weeks, months, years, decades, or even centuries, as the supply in the mantle was almost infinite compared to most magma chambers within the crust at a depth of 2 to 5 kilometers. Some geophysicists could hardly conceal their excitement as they presented this discovery to the media. It was much appreciated news everywhere in Iceland. We all know how much the Eyjafjallajökull eruption did for the economy, and that was a volcano you couldn’t even visit!

A new permanent natural wonder?